Tuning ESIPT fluorophores into dual emitters

Area of Science:

• Photochemistry
• Computational Chemistry
• Materials Science

Background:

• Dyes exhibiting excited-state intramolecular proton transfer (ESIPT) display large Stokes shifts due to significant structural changes after photon absorption.
• Non-quantitative ESIPT can lead to dual emitters with two fluorescence bands, arising from both canonical and ESIPT isomers.
• Achieving dual emission necessitates a precise balance in the relative excited-state free energies of the tautomers, making chemical intuition insufficient for optimization.

Purpose of the Study:

• To computationally investigate a broad range of potential ESIPT/dual emitters with diverse substituents.
• To identify optimal molecular designs and substituent combinations for achieving dual emission.
• To rationalize the influence of different auxochromes on ESIPT and dual emission properties.

Main Methods:

• Utilized quantum-mechanical calculations, specifically time-dependent density functional theory (TD-DFT) and algebraic diagrammatic construction (ADC).
• Validated the computational protocol on known experimental systems.
• Applied the validated protocol to a large, diverse library of novel ESIPT compound candidates.

Main Results:

• The study presents the largest chemical library of potential ESIPT compounds investigated to date.
• Identified specific substituent combinations that are highly promising for developing dual emitters.
• Revealed unexpected synergistic effects between substituents and clarified the impact of auxochromes on dual emission.

Conclusions:

• Computational modeling using TD-DFT and ADC is a robust method for predicting and designing ESIPT/dual emitters.
• The findings provide a rational basis for designing novel fluorescent materials with tunable dual emission properties.
• This work significantly advances the understanding of structure-property relationships in ESIPT dyes for targeted applications.